How is the power linked between the two buildings? They must be served by a single common ground to safely run conductive (CAT5e,6,7) cables between the two.
If they are served by the same electrical meter, then carry on, as long as the electrician did it right you should be ok.
The safest method to run network between buildings is fiber, that way there isn't a conductor between the two. Otherwise you run the risk of differential grounding or EMP from nearby electrical storms frying the equipment at one or both ends of the cable. The longer the run, the higher the risk.